1. Field of the Invention
The present invention is directed to a mechanism of a lens barrel for adjusting a back focus. The adjusting mechanism also protects the lens barrel from being damaged upon impact or upon an excessive load being applied to the lens barrel.
2. Description of Related Art
A lens barrel of a camera is usually fixed to an associated camera body by, for example, a threaded-engagement. In the camera shown in FIG. 3, a lens barrel 51 is connected to a camera body 53 by a female threaded portion 54, which is formed on the inner peripheral surface of a stationary barrel 55 of the camera body 53, and a male threaded portion 56, which is formed on the outer peripheral surface of the lens barrel 51 and is engaged with the female threaded portion 54. In the camera, a back focus (i.e., back focal distance) is adjusted by rotating the lens barrel 51 with respect to the stationary barrel 55, i.e., the camera body 53, to move the lens barrel 51 in tile optical axis direction of the lens barrel 51. After a back focus adjustment is completed, the lens barrel 51 is immovably fixed to the camera body 53 so that the lens barrel 51 will not rotate with respect to the camera body 53, thereby maintaining the back focus adjustment. With this arrangement, however, if the camera 50 is dropped and the lens barrel impacts with the ground, the lens barrel 51 and/or associated members around the lens barrel 51 may be damaged or broken since the impact or load on the lens barrel 51 is not absorbed due to the fixed arrangement of the lens barrel 51 and the camera body 53.